Habitable planets like Earth 'now in the billions'

An international team of astronomers have discovered "billions of planets" not much bigger than Earth and have the potential to sustain life, BBC News reports.

Planets like Earth are circling the faint stars in the Milky Way according to the new research. The estimate for the number of so called "Super-Earths" are based on detections of the number of red-dwarf stars in the Galaxy.

Harps employs an indirect method of detection that infers the existence of orbiting planets from the way their gravity makes a parent star appear to twitch in its motion across the sky.

The team's leader Xavier Bonfils from the Observatoire des Sciences de l'Univers de Grenoble, France said:

"Our new observations with Harps mean that about 40% of all red dwarf stars have a super-Earth orbiting in the habitable zone where liquid water can exist on the surface of the planet.

"Because red dwarfs are so common - there are about 160 billion of them in the Milky Way - this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone."

The team investigated a total of 102 of carefully chosen red dwarfs, which are stars that are dimmer and cooler than our sun.

The team found nine super-earths, which are planets with mass one to ten times the size of Earth, with two of these planets being inside the habitable zone of their stars.

Liquid water is deemed a necessity for life to develop on potentially habitable planets.

"The habitable zone around a red dwarf, where the temperature is suitable for liquid water to exist on the surface, is much closer to the star than the Earth is to the Sun," commented co-researcher Stephane Udry from the Geneva Observatory.

"But red dwarfs are known to be subject to stellar eruptions or flares, which may bathe the planet in X-rays or ultraviolet radiation, and which may make life there less likely."